This invention is in the field of bearings and bearing assemblies. Particularly it is in the field of such assemblies that provide a lock between the shaft and housing of a despin bearing assembly.
No bearing assembly employing the lock function utilizing gallium as the locking medium is known in the art.
Prior lock bearing assemblies have to utilize pyrotechnic devices to disengage the lock which adds complexity and requires frequent replacement of the pyrotechnic devices as well as subjecting the assembly to possible damage.
Still a further disadvantage is that prior art assemblies do not generally provide positive mechanical locking but depend on high friction between surfaces of the locking parts.
Yet a further disadvantage of prior art assemblies is the large amount of energy required to release the lock due to shock impacts between heavy locking members.
Yet still a further disadvantage of prior art assemblies, is that the lock generally displaces the shaft with respect to the housing resulting in chatter and vibration of the assembly members.
Basically, prior art despin bearing assemblies may be described as employing multi-shoe double V-groove clamps which engage matching adjacent flanges on the shaft and housing members. The clamps are attached with redundant explosive bolts which are torqued to very high tension. Squib drivers are used to fire the explosives in the bolts causing them to separate. The loose pieces of the clamp and bolts are pulled away from the flanges with springs and are caught by a clamp catcher fitted with shock absorbing material.
In addition to the disadvantages hereinabove enumerated, the prior art assemblies per se, the clamp and clamp catcher are very heavy, generally between 12 and 19 pounds, the lock assembly consumes a large volume of space, redundant squib drivers are required to fire redundant explosive bolts integral with such assembly, and moreover coefficients of friction and wedge angles of the locking interfaces must be carefully controlled to insure disengagement of the clamp. Hence torsional loads are restrained only by frictional action between the assembly members. This requirement operates to defeat a reliable lock for despin purposes since high friction is needed to carry the torsional loads while inappositely, low friction is required to insure unclamping action.
The risks associated with such designs result in reduction of bearing life because of indiscernable brinnel marks on races and balls of bearings, the possibility of generating metallic debris inside the bearing assembly due to collision of metal parts during vibratory conditions, and possible increase in friction or bearing torque noise caused by damaged races and balls.